Botswana has started erecting a 300-mile electric fence on part of its border with Zimbabwe to stop an influx of humans and livestock, dismaying Zimbabwean officials who claim that southern Africa is building its version of the Israeli security wall.

Almost 8ft high, it will snake through scrubland which acts as a crossing point for refugees and illegal immigrants fleeing economc and political hardships under Robert Mugabe.

Some 100 miles of fence has been erected so far, with some sections already electrified. Botswana hopes to finish construction this year, when immigration officers reinforced by police and army units will patrol the barrier.

Zimbabwean immigrants have torn down parts of the fence and their government has condemned the structure as an affront to human rights which mimics the Israeli attempt to box Palestinians into the West Bank and Gaza strip.

Botswana defended the move yesterday as a legitimate response to the threat posed by diseased cattle and unemployed humans who have illegally crossed the frontier in record numbers since 2000.

Though occupying a larger area, Botswana's population of 1.7 million feels tiny and vulnerable compared to its neighbour's 11.8 million.

The arrival of some 60,000 Zimbabweans has stirred resentment and fuelled claims that many are criminals and spongers.

Authorities in the capital, Gaborone, said it was the biggest immigration problem since independence from Britain in 1966 and that 2,500 people were being repatriated each month.

In the latest apparent sign of being "swamped", mass graves were needed for the "hordes" of unclaimed corpses of illegal immigrants clogging the mortuaries, said Sylvia Muzila, the district commissioner of Francistown, Botswana's second-largest city.

Alfred Dube, Botswana's representative at the UN, told the news agency AFP: "We are concerned about what is going on [in Zimbabwe]. It is very unfortunate that we have our houses being burgled every day and our children being harassed. We understand why our people are saying that Zimbabweans must go."

Residents of Tlokweng, a small village outside Gaborone, turned vigilantes and tried to expel Zimbabweans, derogatively referred to as makwerekwere (foreigners), after blaming them for a spate of robberies and burglaries.

Accusing their hosts of xenophobia, Zimbabweans said they came in search of sanctuary and work, not for trouble.

Construction of the fence started frontier earlier this year. When finished it will stretch from Maitengwe, a village north of Francistown, to Mabata, a camp south of Tuli.

Ties between Gaborone and the Zimbabwean capital, Harare, soured by President Festus Mogae's criticicism of Mr Mugabe's controversial policies, have worsened as a result of the fence.

Zimbabwe's high commissioner in Gaborone, Phelekeza Mphoko, accused Botswana of creating a new Gaza strip. "People will continue to destroy the fence because it has divided families on either side of the border," he told the Botswana Gazette.

Officially the fence is to stop cattle infected with foot and mouth disease. Two outbreaks in two years which hit Botswana's lucrative beef exports to the European Union were sourced to Zimbabwe. Jobs were lost and thousands of cattle slaughtered. Privately, government officials admit the fence is also intended to deter humans. But Mompati Merafhe, the foreign minister, said there was no attempt to seal the border.

"I cannot understand people who say we are trying to close the border with Zimbabwe while we are encouraging Zimbabwean to use the gazetted points of entry. We have more border posts with Zimbabwe than with any other country.

"The construction of the fence must continue and it will continue. We have to go ahead with the fence and when need be, we will open some more border posts."